1. Field of the Invention
The present invention relates to dyes (photosensitizers) for dye-sensitized solar cells and to dye-sensitized solar cells including the same.
2. Description of the Related Art
Diverse research has been carried out in an attempt to develop energy sources that can replace conventional fossil fuels and solve the approaching energy crisis. Particularly, extensive research is underway to find ways of using alternative energy sources, such as wind power, atomic power, and solar power, as substitutes for petroleum resources, which are expected to be depleted within several decades. Among these alternative energy sources, solar cells use solar energy, which is infinite and environmentally friendly, unlike other energy sources. Since 1983, when Si solar cells were first produced, solar cells have been emphasized, and Si solar cells have recently drawn attention from researchers.
However, practical use of Si solar cells is difficult due to high production costs and challenges in improving cell efficiency. Accordingly, researchers are focusing on the development of dye-sensitized solar cells that can be produced at low cost.
Unlike the Si solar cell, the dye-sensitized solar cell is an electrochemical solar cell mainly composed of photosensitive dye molecules that absorb visible rays and produce electron-hole pairs, and a transition metal oxide that transfers the produced electrons. Dye-sensitized solar cells can be produced at low cost, and since they use transparent electrodes, the cells can be applied to the external glass walls of a building or glass greenhouse. However, dye-sensitized solar cells have limited practical application due to their low photoelectric efficiency.
The photoelectric efficiency of a solar cell is proportional to the quantity of electrons produced from the absorption of solar beams. Thus, to increase the photoelectric efficiency, the quantity of electrons should be increased, or the produced and excited electrons should be prevented from being used to cause electron-hole recombination. The quantity of produced electrons can be increased by raising the absorption of solar beams or the dye adsorption efficiency.
Particles of an oxide semiconductor should be nano-sized to increase the dye adsorption efficiency of each unit area. The reflectivity of a platinum electrode should be increased, or a micro-sized oxide semiconductor light scattering agent should be included to increase the absorption of solar beams. However, these conventional methods have limitations in increasing the photoelectric efficiency of solar cells.